Scanning device, apparatus and method for image processing

ABSTRACT

A scanning device includes a first scanning unit, a second scanning unit, and a light source corresponding to each of the first scanning unit and the second scanning unit. The light sources are arranged on the same side of the first and second scanning units with respect to the main scanning direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technology for scanning the front andthe back surfaces of a paper.

2. Description of the Related Art

Various approaches have been taken to reduce the size of a scanningdevice. For example, use of a contact image sensor (CIS), use a CIShaving fewer light emitting diodes (LEDs), etc. helps to reduce the sizeof a scanning device.

FIG. 7A is a schematic diagram of a conventional CIS 1. FIG. 7B is aside view of the conventional CIS 1 taken along a line A-A shown in FIG.7A. FIG. 7C is a schematic diagram for explaining scanning operationperformed by the conventional CIS 1.

The CIS 1 includes a light source 11 arranged at a first end in a mainscanning direction. Although not shown, the light source 11 includesthree-color LEDs, i.e., a red LED that emits a red light beam, a greenLED that emits a green light beam, and a blue LED that emits a bluelight beam. When the CIS 1 scans a surface of a printed paper 20 by eachline, each of the three LEDs emits a light beam of corresponding colorin the time division manner. The light beam then passes through a lightguide plate 12, so that the light beam is uniformly projected onto theprinted paper 20. The printed paper 20 reflects the light beam. A rodlens array 13 collects the reflected light beam, and converges thereflected light beam onto the line sensor 14 by each pixel. Aphotoelectric conversion element (not shown) included in the line sensor14 converts the received light beam into an electric signal.

As shown in FIG. 7A, because the light source 11 is arranged at thefirst end, the center of the CIS 1 and the center of a scanning unit(the line sensor 14) are located in different positions in the mainscanning direction.

The CIS 1 scans a surface of the printed paper 20 by each line in themain scanning direction, i.e., the CIS 1 scans each line from the firstpixel arranged at the first end, to the last pixel arranged at a secondend opposite to the first end. As shown in FIG. 7C, when the CIS 1finishes scanning one line, the printed paper 20 is moved over the CIS 1in a direction perpendicular to the main scanning direction, i.e., asub-scanning direction, for a distance equivalent to one line. The CIS 1then scans the next line on the surface of the printed paper 20.

Japanese Patent Application Laid-open No. 2006-140902 discloses aconventional scanning device including two CISs that concurrently scanthe front and the back surfaces of a printed paper. Specifically, asshown in FIGS. 8A to 9C, a first CIS 2 and a second CIS 3 are arrangedin such a manner that the first CIS 2 faces the front surface of theprinted paper 20 and the second CIS 3 faces the back surface of theprinted paper 20. The printed paper 20 is supplied from a paper feedtray (not shown), and the printed paper is conveyed between the firstCIS 2 and the second CIS 3. Then, the first CIS 2 and the second CIS 3concurrently scan the front and the back surfaces of the printed paper20.

FIG. 8A is a schematic diagram for explaining an arrangement of thefirst CIS 2 and the second CIS 3. The first CIS 2 is arranged to facethe front surface, and the second CIS 3 is arranged to face the backsurface of the printed paper 20. The first CIS 2 scans the front surfacethereby obtaining an image of the front surface, and the second CIS 3scans the back surface thereby obtaining an image of the back surface.The first CIS 2 scans the front surface in a forward direction, which isa direction from left to right, with respect to the front surface. Thesecond CIS 3 scans the back surface in the forward direction, which is adirection from left to right, with respect to the back surface. In otherwords, scanning directions of the first CIS 2 and the second CIS 3 areopposite. Therefore, a light source 110 of the first CIS 2 and a lightsource 111 of the second CIS 3 are arranged at the opposite ends in themain scanning direction.

Because the light sources 110 and 111 are arranged at the opposite endsin the main scanning direction, undesired spaces indicated by two-headedarrows A are formed in the main scanning direction. As a result, thewidth of the scanning device increases.

As shown in FIG. 8B, the first CIS 2 and the second CIS 3 can bearranged in such a manner that the centers of the first CIS 2 and thesecond CIS 3 are located in the same position so that an undesired spaceis not formed in the main scanning direction. In this arrangement,however, the first CIS 2 cannot scan a part of the front surface of theprinted paper indicated by a two-headed arrow B1, and the second CIS 3cannot scan a part of the back surface of the printed paper indicated bya two-headed arrow B2.

FIGS. 9A to 9C are schematic diagrams for explaining the depth requiredfor arranging the first CIS 2 and the second CIS 3. The depth is thedistance in the sub-scanning direction. As shown in FIG. 9A, each of thefirst CIS 2 and the second CIS 3 is generally provided with a whitereference portion 25 that generates white reference data to be used forshading correction performed by the scanning device. As shown in FIG.9B, the first CIS 2 and the second CIS 3 can be arranged close to eachother, thereby reducing the depth required for arrangement of the firstCIS 2 and the second CIS 3. However, the white reference portions 25 arerequired to be arranged in such a manner that the white referenceportion 25 of the first CIS 2 is not affected by a light beam emittedfrom the light source 11 of the second CIS 3, and the white referenceportion 25 of the second CIS 3 is not affected by a light beam emittedfrom the light source 11 of the first CIS 2.

As shown in FIG. 9C, the first CIS 2 and the second CIS 3 can bearranged such that they are almost above/below each other. With thisarrangement, the depth required for the first CIS 2 and the second CIS 3can be reduced to the minimum, however, there is no space for arrangingthe white reference portions 25. Therefore, calibration data used forshading correction is stored in a memory (not shown) of the scanningdevice, which causes increase of costs. In addition, the calibrationoperation must be performed manually such that a sheet of paper isscanned and the image data is processed, which causes inconvenience to auser.

In this manner, in the scanning device shown in FIGS. 8A to 9C,undesired spaces are formed in the sub-scanning direction, and the widthof the scanning device increases. Moreover, either spaces are requiredfor arranging the white reference portions, or a memory is required forstoring calibration data.

In recent years, improvements have been made in a portable computer anda portable scanning device. A user can carry a scanning device togetherwith a portable computer, such as a laptop computer or a mobilecomputer. Therefore, there is a need of improving a technology forreducing the size of a scanning device.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

According to an aspect of the present invention, there is provided ascanning device including a first scanning unit that scans a firstsurface of a scan-target medium along a scanning direction to obtain afirst image; a second scanning unit that scans a second surface of thescan-target medium along the scanning direction to obtain a secondimage; and at least one light source that emits a light beam on thefirst surface while the first scanning unit is scanning the firstsurface and emits a light beam on the second surface while the secondscanning unit is scanning the second surface, wherein the light sourceis arranged at one side of the scanning direction.

According to another aspect of the present invention, there is providedan image processing method including acquiring a first image of a firstsurface of a scan-target medium and a second image of a second surfaceof the scan-target medium by using a scanning device including a firstscanning unit that scans a first surface of a scan-target medium along ascanning direction to obtain a first image; a second scanning unit thatscans a second surface of the scan-target medium along the scanningdirection to obtain a second image; and at least one light source thatemits a light beam on the first surface while the first scanning unit isscanning the first surface and emits a light beam on the second surfacewhile the second scanning unit is scanning the second surface, whereinthe light source is arranged at one side of the scanning direction; andprocessing and outputting the first image and the second image.

According to still another aspect of the present invention, there isprovided an image processing apparatus including a scanning deviceincluding a first scanning unit that scans a first surface of ascan-target medium along a scanning direction to obtain a first image; asecond scanning unit that scans a second surface of the scan-targetmedium along the scanning direction to obtain a second image; and atleast one light source that emits a light beam on the first surfacewhile the first scanning unit is scanning the first surface and emits alight beam on the second surface while the second scanning unit isscanning the second surface, wherein the light source is arranged at oneside of the scanning direction; a supplying unit that supplies thescan-target medium to the scanning device; a discharge unit thatdischarges the scan-target medium from the scanning device; and aninformation processing device that processes and outputs the first imageand the second image.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a scanning device according to anembodiment of the present invention;

FIG. 2 is a schematic diagram for explaining an arrangement of a firstCIS and a second CIS of the scanning device;

FIGS. 3A and 3B are schematic diagrams of other examples of arrangementof the first CIS and the second CIS;

FIG. 4 is a schematic diagram for explaining the depth required forarranging the first CIS and the second CIS;

FIGS. 5A to 5E are schematic diagrams for explaining image processingperformed by the scanning device;

FIG. 6 is a block diagram of an image processing apparatus according tothe embodiment;

FIGS. 7A to 7 c are schematic diagrams for explaining a conventionalscanning device;

FIGS. 8A and 8B and FIGS. 9A to 9C are schematic diagrams for explaininganother conventional scanning device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are explained in detailbelow with reference to the accompanying drawings.

The same reference numerals are used for components that have the samefunction as those in the above conventional scanning device, anddetailed descriptions of such components are omitted.

FIG. 1 is a schematic diagram of a scanning device according to anembodiment of the present invention. The first CIS 2 is arranged to facethe front surface of the printed paper 20, and the second CIS 3 isarranged to face the back surface of the printed paper 20. The first CIS2 and the second CIS 3 concurrently scan the front and the back surfacesthereby obtaining images of the printed paper 20. The first CIS 2 scansthe front surface in the forward direction with respect to the frontsurface, and the second CIS 3 scans the back surface in a backwarddirection, which is a direction opposite to the forward direction, withrespect to the back surface. In other words, the scanning directions ofthe first CIS 2 and the second CIS 3 are the same.

The scanning device includes an auto document feeder (ADF). The ADF isoperated as described below. A pile of the printed papers 20 is stackedon a hopper (not shown). Each of the printed papers 20 is pulled outfrom the bottom of the pile by a pick roller 26 and a separation pad 27,and the pulled-out printed paper 20 is fed to a pair of conveyingrollers 28 a one by one. The hopper can be retractable. If the hopper isretractable, the hopper is retracted inside the scanning device when thescanning device is not in use or the scanning device is carried by auser.

The conveying rollers 28 a and a pair of conveying rollers 28 b conveythe printed paper 20 between the first CIS 2 and the second CIS 3. Whenthe first CIS 2 and the second CIS 3 finish scanning one line on asurface of the printed paper 20, the conveying rollers 28 a and 28 bmove the printed paper 20 in the sub-scanning direction for a distanceequivalent to one line. The sub-scanning direction is a directionperpendicular to the main scanning direction. Each of the first CIS 2and the second CIS 3 then scans the next line on the surface of theprinted paper 20. When each of the first CIS 2 and the second CIS 3finishes scanning the front and the back surfaces of the printed paper20, the conveying rollers 28 b discharge the printed paper 20 out of thescanning device.

The first CIS 2 includes a light source 21 and the second CIS 3 includesa light source 31. The light sources 21 and 31 are arranged at the sameend in the main scanning direction. The first CIS 2 and the second CIS 3can have different outer shapes and dimensions under conditions the mainscanning directions of the first CIS 2 and the second CIS 3 are thesame.

FIG. 2 is a schematic diagram of arrangement of the first CIS 2 and thesecond CIS 3. FIGS. 3A and 3B are schematic diagrams of other examplesof arrangement of the first CIS 2 and the second CIS 3. The first CIS 2is arranged to face the front surface, and the second CIS 3 is arrangedto face the back surface of the printed paper 20.

As shown in FIG. 2, the centers of the first CIS 2 and the second CIS 3are located at the same position in the main scanning direction. Thecenters of the scanning units (the line sensors 14) of the first CIS 2and the second CIS 3 are located at the same position in the mainscanning direction. With this configuration, the spaces indicated by thearrows A shown in FIG. 8A can be eliminated. As a result, the width ofthe scanning device can be reduced. Furthermore, the areas indicated bythe arrows B1, B2 shown in FIG. 8B can be eliminated.

Although not shown, each of the light sources 21 and 31 includesthree-color LEDs, i.e., a red LED that emits a red light beam, a greenLED that emits a green light beam, and a blue LED that emits a bluelight beam. When each of the first CIS 2 and the second CIS 3 scans asurface of the printed paper 20 by each line, each of the three LEDsemits the light beam to each line in the time division manner. The lightbeam then passes through the light guide plate 12, so that the lightbeam is uniformly projected onto the printed paper 20. The printed paper20 reflects the light beam. The rod lens array 13 collects the reflectedlight beam, and converges the reflected light beam onto the line sensor14 by each pixel. A photoelectric conversion element (not shown)included in the line sensor 14 converts the received light beam into anelectric signal.

The second CIS 3 scans the back surface of the printed paper 20 in thebackward direction with respect to a scanned surface of the printedpaper 20, while the first CIS 2 scans the front surface of the printedpaper 20 in the forward direction with respect to a scanned surface ofthe printed paper 20. As a result, an image acquired by the second CIS 3is a mirrored image of the image printed on the printed paper 20.Therefore, an image acquired by the second CIS 3 needs to be inverted by180 degrees.

Although a configuration is explained above in which the first CIS 2scans the front surface of the printed paper 20 and the second CIS 3scans the back surface, the present invention is not limited to thisconfiguration. For example, a surface of the printed paper 20 to bescanned by each of the first CIS 2 and the second CIS 3 can bedetermined depending on a conveying direction of the printed paper 20,or whether the printed paper 20 is pulled out from the top or the bottomof a pile of the printed papers 20 when the printed paper 20 is suppliedfrom a paper feeding side.

Although a configuration is explained above in which two light sources21 and 31 are used, it is possible to use a common light source for thefirst CIS 2 and the second CIS 3. As shown in FIG. 3A, the first CIS 2,the second CIS 3, and a common light source 41 can be formed as onepiece. On the contrary, as shown in FIG. 3B, the first CIS 2, the secondCIS 3, and a common light source 51 can be formed as separate pieces. Inboth cases, the centers of the first CIS 2 and the second CIS 3 arelocated at the same position, and the centers of the scanning units (theline sensors 14) of the first CIS 2 and the second CIS 3 are located atthe same position.

Although not shown, each of the light sources 21 and 31 includesthree-color LEDs, i.e., a red LED that emits a red light beam, a greenLED that emits a green light beam, and a blue LED that emits a bluelight beam. When each of the first CIS 2 and the second CIS 3 scans asurface of the printed paper 20 by each line, each of the three LEDsemits the light beam to each line in the time division manner. The lightbeam then passes through the light guide plate 12, so that the lightbeam is uniformly projected onto the printed paper 20. The printed paper20 reflects the light beam. A rod lens array 13 collects the reflectedlight beam, and converges the reflected light beam onto the line sensor14 by each pixel. A photoelectric conversion element (not shown)included in the line sensor 14 converts the light beam into an electricsignal.

FIG. 4 is a schematic diagram for explaining the depth required forarranging the first CIS 2 and the second CIS 3. Because the first CIS 2and the second CIS 3 face to each other, the depth required for thefirst CIS 2 and the second CIS 3 is reduced to the minimum. The whitereference portions 25 for the first CIS 2 and the second CIS 3 arearranged to a position closest to each other out of positions in whichthe white reference portion 25 of the first CIS 2 is not affected by alight beam emitted from the light source 11 of the second CIS 3, and thewhite reference portion 25 of the second CIS 3 is not affected by alight beam emitted from the light source 11 of the first CIS 2.

FIGS. 5A to 5E are schematic diagrams for explaining image processingperformed by the scanning device. As shown in FIG. 5A, the scanningdevice concurrently scans the front and the back surfaces of the printedpaper 20. Alternatively, as shown in FIG. 5B, the printed paper 20 isfolded in two, and both surfaces of the folded printed paper 20 can beconcurrently scanned by the scanning device.

As shown in FIG. 5C, when each of the first CIS 2 and the second CIS 3scans one line of the printed paper 20, each of the three LEDs emits thelight beam to the line in the time division manner. In this manner, thefirst CIS 2 scans the front surface of the printed paper 20 and thesecond CIS 3 scans the back surface of the printed paper 20. Althoughthe two CISs 2 and 3 are provided, it is possible to operate only one ofthe CISs 21 and 31 at a time.

As shown in FIG. 5D, an image acquired by the first CIS 2 is output as anormal image. On the other hand, an image acquired by the second CIS 3is output as a mirrored image. As shown in FIG. 5E, the mirrored imageis inverted by 180 degrees, and turned into a normal image. Thus, thefront and the back surfaces of the printed paper 20 can be output asnormal images.

Inversion of a mirrored image can be performed by the scanning device.Alternatively, inversion of a mirrored image can be performed by usingan external information processing device. Moreover, inversion of anentire mirrored image can be performed by at a time. Alternatively, amirrored image can be inverted line by line.

It is possible to configure such that the scanning directions of thefirst CIS 2 and the second CIS 3 are opposite so that the imagesacquired by both the first CIS 2 and the second CIS 3 are normal images.In other words, when such a configuration is adopted, it is notnecessary to invert an image.

FIG. 6 is a schematic diagram of an image processing apparatus accordingto the embodiment. The image processing apparatus includes a scanningdevice 50 and an information processing device 60. The scanning device50 scans the front and the back surfaces of the printed paper 20 toobtain images of the printed paper 20. Upon receiving a signalrepresenting a scanned image from the scanning device 50, theinformation processing device 60 processes the received signal. Thescanning device 50 includes a control unit 51 and an interface (I/F)unit 58 for input and output of data.

The control unit 51 stores therein computer programs for implementingvarious processes performed by the scanning device 50, and causes thescanning device 50 to perform the processes. The control unit 51includes a driving unit 52, a scanning unit 53, a storage unit 56, andan image output unit 57. The driving unit 52 causes the ADF using amotor (not shown) to pull out a printed paper from a pile of printedpapers one at a time and feed the pulled-out paper to the scanning unit53. Furthermore, when the scanning unit 53 finishes scanning one line ofthe printed paper, the driving unit 52 causes the ADF to move theprinted paper in the sub-scanning direction to an extremely slightdegree. When the scanning unit 53 finishes scanning the surfaces of theprinted paper, the driving unit 52 causes the ADF to discharge theprinted paper from the scanning device 50.

The scanning unit 53 includes a first scanning unit 54 and a secondscanning unit 55. The first scanning unit 54 includes the light source21 and a scanning element array (the rod lens array 13), and the secondscanning unit 55 includes the light source 31 and a scanning elementarray (the rod lens array 13). The light sources 21 and 31 are arrangedat the same end of each of the first scanning unit 54 and the secondscanning unit 55. The first scanning unit 54 and the second scanningunit 55 concurrently scan the front and the back surfaces of the printedpaper. The first scanning unit 54 scans the front surface in the forwarddirection with respect to the front surface, and the second scanningunit 55 scans the back surface in the backward direction with respect tothe back surface. In other words, the scanning directions of the firstCIS 2 and the second CIS 3 are the same. The storage unit 56 temporarilystores images scanned by the first scanning unit 54 and the secondscanning unit 55. The image output unit 57 sends the images stored inthe storage unit 56 to the information processing device 60 through theI/F unit 58.

The information processing device 60 includes a control unit 61 and anI/F unit 66 for input and output of data. The control unit 61 storestherein computer programs for implementing various processes performedby the information processing device 60, and causes the informationprocessing device to perform various processes. The control unit 61includes an image receiving unit 62, a storage unit 63, an imageinverting unit 64, and an image output unit 65. The image receiving unit62 receives images scanned by the scanning unit 53 from the scanningdevice 50 via the I/F unit 66, and temporarily stores the receivedimages into the storage unit 63. The images stored in the storage unit63 include a normal image and a mirrored image of the printed paper.

The image inverting unit 64 inverts a mirrored image of the printedpaper stored in the storage unit 63 by 180 degrees, so that the mirroredimage is turned into a normal image. After that, the image invertingunit 64 stores the images on the front and the back surfaces of theprinted paper in a state of normal images into the storage unit 63. Theimage output unit 65 outputs that images as normal images to a displaydevice (not shown).

According to an aspect of the present invention, it is possible toreduce the overall size of a scanning device.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

1. A scanning device comprising: a first scanning unit that scans afirst surface of a scan-target medium along a scanning direction toobtain a first image; a second scanning unit that scans a second surfaceof the scan-target medium along the scanning direction to obtain asecond image; and at least one light source that emits a light beam onthe first surface while the first scanning unit is scanning the firstsurface and emits a light beam on the second surface while the secondscanning unit is scanning the second surface, wherein the light sourceis arranged at one side of the scanning direction.
 2. The scanningdevice according to claim 1, wherein the first scanning unit scans thefirst surface in a first scanning direction along the scanning directionto obtain the first image, the second scanning unit scans the secondsurface in the first scanning direction along the scanning direction toobtain the second image, and the scanning device further comprising aninformation processing unit that performs a processing for inverting thefirst image relative to the second image by 180 degrees.
 3. The scanningdevice according to claim 1, wherein the first scanning unit scans afront surface of the scan target medium as the first surface and thesecond scanning unit scans a back surface of the scan target medium asthe second surface.
 4. The scanning device according to claim 1, whereinthe scan target medium is folded into two, and the first scanning unitscans a front surface of folded scan target medium as the first surfaceand the second scanning unit scans a back surface of the scan targetmedium as the second surface.
 5. The scanning device according to claim1, wherein the light source is common to the first scanning unit and thesecond scanning unit.
 6. The scanning device according to claim 1,further comprising white reference portions that are used forcalibration, wherein the white reference portions including a firstwhite reference portion corresponding to the first scanning unit, thefirst white reference portion being laid on a level on which a scanningsurface of the second scanning unit falls; and a second white referenceportion corresponding to the second scanning unit, the second whitereference portion being laid on a level on which a scanning surface ofthe first scanning unit falls.
 7. The scanning device according to claim1, wherein the first scanning unit and the second scanning unitconcurrently scan the first surface and the second surface.
 8. Thescanning device according to claim 1, wherein the light source includesa first light source corresponding to the first scanning unit and asecond light source corresponding to the second scanning unit.
 9. Animage processing method comprising: acquiring a first image of a firstsurface of a scan-target medium and a second image of a second surfaceof the scan-target medium by using a scanning device including a firstscanning unit that scans a first surface of a scan-target medium along ascanning direction to obtain a first image; a second scanning unit thatscans a second surface of the scan-target medium along the scanningdirection to obtain a second image; and at least one light source thatemits a light beam on the first surface while the first scanning unit isscanning the first surface and emits a light beam on the second surfacewhile the second scanning unit is scanning the second surface, whereinthe light source is arranged at one side of the scanning direction; andprocessing and outputting the first image and the second image.
 10. Theimage processing method according to claim 9, wherein the first scanningunit scans the first surface in a first scanning direction along thescanning direction to obtain the first image, the second scanning unitscans the second surface in the first scanning direction along thescanning direction to obtain the second image, and the processingincludes inverting the first image relative to the second image by 180degrees.
 11. An image processing apparatus comprising: a scanning deviceincluding a first scanning unit that scans a first surface of ascan-target medium along a scanning direction to obtain a first image; asecond scanning unit that scans a second surface of the scan-targetmedium along the scanning direction to obtain a second image; and atleast one light source that emits a light beam on the first surfacewhile the first scanning unit is scanning the first surface and emits alight beam on the second surface while the second scanning unit isscanning the second surface, wherein the light source is arranged at oneside of the scanning direction; a supplying unit that supplies thescan-target medium to the scanning device; a discharge unit thatdischarges the scan-target medium from the scanning device; and aninformation processing device that processes and outputs the first imageand the second image.
 12. The image processing apparatus according toclaim 11, wherein the first scanning unit scans the first surface in afirst scanning direction along the scanning direction to obtain thefirst image, the second scanning unit scans the second surface in thefirst scanning direction along the scanning direction to obtain thesecond image, and the information processing device performs aprocessing for inverting the first image relative to the second image by180 degrees.
 13. The image processing apparatus according to claim 11,wherein the information processing device includes a receiving unit thatreceives the first image and the second image from the scanning device;an image inverting unit that performs a processing for inverting thefirst image relative to the second image; and an image output unit thatoutputs inverted first image and the second image.
 14. The imageprocessing apparatus according to claim 11, wherein the first scanningunit and the second scanning unit concurrently scan the first surfaceand the second surface.
 15. The image processing apparatus according toclaim 11, wherein the light source includes a first light sourcecorresponding to the first scanning unit and a second light sourcecorresponding to the second scanning unit.
 16. The image processingapparatus according to claim 11, wherein the light source is common tothe first scanning unit and the second scanning unit.
 17. The imageprocessing apparatus according to claim 11, wherein the first scanningunit scans the first surface in a first scanning direction along thescanning direction to obtain the first image, and the second scanningunit scans the second surface in a second scanning direction, which isopposite to the first scanning direction, along the scanning directionto obtain the second image.